To my mind one of the issues is the "random check" of visibility. It´s totally absurd to make it in several circumstances (ie at close distance in clear terrain). Conscripts or veterans, soldiers have eyes. The other day one of my units couldn´t see from the top of a mountain a large group of enemy tanks and infantry approaching in clear terrain because I was a conscript. Instead, they detected my unit even though it was in a forest.
It doesn´t matter if the game has complex formulas or amazing combat rules, because visibility affects decisively to engagements. Basically, it is needed a bit of common sense and a more complete information about the rules we are playing.
Another issue I´ve detected is combat with tanks, I noticed most of them are destroyed wiht one shot. Consider Combat Mission rules should be designed according to reality, never to war movies or spectacular explosions. That´s Ok if Battlefront decide to follow this path but they shouldn´t sell it like a realistic game. Oh no.